XML 186 R158.htm IDEA: XBRL DOCUMENT
v3.20.4

Credit Facilities, Long-Term Debt and Lease Liabilities - Letters of Credit (Details) - CAD ($) | Dec. 31, 2020 | Dec. 31, 2019
--- | --- | ---
Letter of credit |  |
Disclosure of detailed information about borrowings [line items] |  |
Exposure to credit risk on loan commitments and financial guarantee contracts | $ 621,000,000 | $ 690,000,000
Amount exercised under letters of credit | 0 | $ 0
Committed bilateral credit facilities |  |
Disclosure of detailed information about borrowings [line items] |  |
Maximum borrowing capacity under line of credit | 240,000,000 |
Uncommitted demand letter facility |  |
Disclosure of detailed information about borrowings [line items] |  |
Maximum borrowing capacity under line of credit | 100,000,000 |
Uncommitted demand letter facility | TransAlta Renewables Inc. |  |
Disclosure of detailed information about borrowings [line items] |  |
Maximum borrowing capacity under line of credit | $ 100,000,000 |

X
- Definition Line items represent concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes of the table. + References No definition available. + Details
Name: | ifrs-full_DisclosureOfDetailedInformationAboutBorrowingsLineItems
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The amount of the exposure to credit risk on loan commitments and financial guarantee contracts. [Refer: Loan commitments [member]; Financial guarantee contracts [member]; Credit risk [member]] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IFRS -Number 7 -IssueDate 2019-01-01 -Paragraph 35H -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=7&code=ifrs-tx-2019-en-r&anchor=para_35H&doctype=Standard -URIDate 2019-03-27 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Name IFRS -Number 7 -IssueDate 2019-01-01 -Paragraph 35I -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=7&code=ifrs-tx-2019-en-r&anchor=para_35I&doctype=Standard -URIDate 2019-03-27 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Name IFRS -Number 7 -IssueDate 2019-01-01 -Paragraph 35M -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=7&code=ifrs-tx-2019-en-r&anchor=para_35M&doctype=Standard -URIDate 2019-03-27 + Details
Name: | ifrs-full_ExposureToCreditRiskOnLoanCommitmentsAndFinancialGuaranteeContracts
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amounts Exercised Under Letters Of Credit + References No definition available. + Details
Name: | tac_AmountExercisedUnderLettersOfCredit
Namespace Prefix: | tac_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Line Of Credit Facility, Maximum Borrowing Capacity + References No definition available. + Details
Name: | tac_LineOfCreditFacilityMaximumBorrowingCapacity1
Namespace Prefix: | tac_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Details
Name: | ifrs-full_ClassesOfFinancialInstrumentsAxis=tac_LetterofCreditMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_BorrowingsByNameAxis=tac_CommittedBilateralCreditFacilitiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_BorrowingsByNameAxis=tac_UncommittedDemandLetterFacilityMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_SignificantInvestmentsInSubsidiariesAxis=tac_TransAltaRenewablesInc.Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |